Recent years have seen the development of a microscope apparatus that projects interference fringes as structured illumination light onto a specimen and that makes it possible to analyze the structure of the specimen at a resolution higher than the resolution limit of the objective lens by analyzing images captured of moiré fringes arising due to the interference fringes and the structure of the specimen (for example, refer to patent documents 1 and 2 and non-patent document 1 cited below).
In the microscope apparatus according to the prior art, light from a light source is diffracted into three different directions, from among which a pair of +1st order and −1st order diffracted light beams diffracted in one direction is selected using a shutter, and after converting each beam to S-polarized light, the beams are made to interfere with each other on the specimen, thus forming interference fringes on the specimen. Then, a plurality of image capturing operations are performed while varying the phase difference between the +1st order diffracted light beam and the −1st order diffracted light beam on the specimen, and the images of the moiré fringes are analyzed to obtain a super-resolution image of the specimen with a resolution higher than the resolution limit of the objective lens.